There is a centripetal type screen apparatus in which a stirring member (e.g., foil, agitator or the like) is located inside a cylindrical screen provided in a tank, paper raw materials are allowed to flow from inside to outside of the screen, and foreign matters are removed from the paper raw materials.
In such a screen apparatus, when the paper raw materials flow from inside to outside of the screen and foreign matters are removed from the paper raw materials, it is easy to pass through a screen located upstream of the paper raw materials, and a screen located more downstream of the paper raw materials has higher density in the paper raw materials and it becomes more difficult to pass through such a screen and thus, selection efficiency is deteriorated.
In such a case, in the centripetal type screen apparatus which rotates outside and near the screen, it is possible to supply dilute water to a primary chamber located on the supply side of the paper raw materials.
In the centripetal type screen apparatus, however, even if dilute water is provided while passing through the tank, there is a problem that a portion of the dilute water passing through the tank does not exhibit an effect of dilution in a secondary chamber of selected paper raw materials.